Skip stitch attachments for zigzag sewing machines



J. c. SECK 3,386,399

SKIP STITCH ATTACHMENTS FOR ZIGZAG SEWING MACHINES June 4, 1968 2 Sheets-Sheet 1 Filed Aug. 25, 1966 mvzzmon. John C. Seck IIllIlIlllllII/n J. C. SECK June 4, 1968 SKIP STITCH ATTACHMENTS FOR ZIGZAG SEWING MACHINES 2 Sheets-Sheet .2 7

Filed Aug. 23, 1966 INYENTOR. John C, Seek A oRNEy- WITNES United States Patent 3,386,399 SKIP STITCH ATTACHMENTS FOR -ZIGZAG SEWING MACHINES John C. Seck, Colonia, N.J., assignor to The Singer Company, New York, N.Y., a corporation of New Jersey Filed Aug. 23, 1966, Ser. No. 574,406 Claims. (Cl. 112154) This invention relates to skip stitch atach-ments for zigzag sewing machines and more particularly to a skip stitch attachment which when connected to the needle bar of a zigzag sewing machine equipped with a blind-stitch pat tern cam sews only the crossover stitches.

In a zigzag sewing machine in which needle jogging can be controlled to form a blind-stitch, a plurality of rightmost stitches can be formed for each leftmost stitch. If it were possible to skip the rightmost stitches, a desirable long, loose basting stitch seam would be formed.

It is, therefore, an object of this invention to provide an atachment for a zigzag sewing machine which will cause skipped stitches when the needle is in either its rightmost or its leftmost position.

Another object of this invention is to provide a skip stitch attachmeht for a zigzag sewing machise in accordance with the foregoing object in which needle jogging if the sewing machine can be controlled to form a blindstitch.

Another object of this invention is to provide a skip stitch attachment in accordance with the foregoing objects in which the skip stitch attachment is simple, inexpensive and effective.

The objects of the invention are accomplished by providing a skip stitch attachment which includes a collar by which it is clamped to the needle bar of a zigzag sewing machine by a thumbscrew. Pivotally hinged on the collar is a wire bell crank. The wire bell crank includes a rearwardly extending arm which frictionally engages the side of the presser bar sleeve, but only when the needle is in its rightmost position. A forwardly extending arm of the wire bell crank is disposed horizontally parallel to the front surface of the collar, and a coil spring having an eyelet formed at its free end depends from the collar. The needle thread is threaded between the forward-1y extending arm of the bell crank and the front surface of the collar, and then through the eyelet of the coil spring. When the needle is in its rightmost position, the rearwardly extending arm of the bell crank frictionally engages the side of the presser bar sleeve to pivot the bell crank so that its forwardly extending arm nips the needle thread against the front surface of the collar. Nipping of the thread in conjunction with the coil spring which acts as a thread take-up keeps the thread to the needle taut. Therefore, loops of thread cannot form at the eye of the needle for seizure by the hook beak of the loop take-r, and skipped stitches result. When the needle is in its leftmost position, stitches are formed as usual because the rearwardly extending arm of the bell crank is out of contact with the presser bar sleeve. Since stitches are formed only during the intermittent leftmost penetrations of the needle, a desirable long, loose basting stitch seam can be formed.

Other objects and a fuller understanding of the invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawings in which:

FIG. 1 is a front elevational view of the stitch forming area of a zigzag sewing machine incorporating the attachment of the invention with the needle bar in its leftmost or stitch-producing position;

FIG. 2 is a left-end elevational view of the stitch-forming :area of FIG. 1;

- Patented June 4, 1968 ice FIG. 3 is a front elevational view of the stitch-forming area of a zigzag sewing machine incorporating the attachment of the invention with the needle bar in its rightmost or stitch-skipping position;

FIG. 4 is a left-end elevational view of the stitchforming area of FIG. 3;

FIG. 5 is a cross-sectional view taken along the line 5-5 in FIG. 4;

FIG. 6 is a front perspective view of the attachment of the invention;

FIG. 7 is a top plan view of a needle-jogging mechanism equipped with a blind stitch pattern cam; and

FIG. 8 is a top perspective view of a portion of two plies of fabric containing a basting stitch seam produced by the attachment of the invention.

With reference to the drawings, .the invention is illustrated as attached to a zigzag sewing machine having a frame of which only portions of the sewing head 20 and the work-supoprting bed 21 are shown. A needle aperture 22 is formed in the work-supporting bed.

Mounted in the work-supporting bed 21 is a work feed mechanism represented by a feed dog 23 having feed teeth 25. Also mounted in the work-supporting bed is a needle thread loop-seizing means represented by a vertical axis loop taker 26 of which only a portion is shown. The loop taker has a hook beak 27 and is driven through a vertical axis loop taker shaft 28.

A needle bar 29 is mounted in the sewing head 20 in a needle bar gate 32. Held in a needle clamp 33 at the exterior end of the needle bar by a thumbscrew 34 is a needle 36 having an eye 37. A hook-shaped thread guide 38 is connected to the needle bar just above the needle clamp 33 by a screw 39.

Reciprocating motion is imparted to the needle bar 29 throguh a crank mechanism indicated generally at 40 on an arm shaft 44. Lateral jogging motion is imparted to the needle bar through a needle-jogging mechanism indicated generally at 45. Generally, the needle jogging mechanism includes a pattern cam 46, a pair of carn followers 47 and 48, a wobble plate 43 which integrates the motions of the cam followers, and a connecting rod 50 between the wobble plate and the needle bar gate 32. The needle-jogging mechanism 45 is described in detail in a United States patent of R. E. Johnson, No. 2,862,468, granted Dec. 2, 1958. As used with the present invention, the pattern cam 46 has a blind-stitch pattern. It is understood that other types of needle-jogging mechanisms than that shown are equally well suited for use with the present invention.

Mounted in the sewing head 20 behind the needle bar 29 is a presser bar sleeve 52. The presser bar sleeve guides a presser bar 53. Connected to the external end of the presser bar by a thumbscrew 54 is a presser foot 55.

A skip stitch attachment indicated generally at 56 includes a C-shaped collar 57 through which it is clamped to the needle bar 29 above the needle clamp 33 by a thumbscrew 58. Pivotally hinged on the collar 57 is a wire bell crank 59. The wire bell crank is hinged on the collar through a horizontal intermediate portion 61 which is fulcrumed in a roll pin 62 in a groove 63 in the top of the collar.

The wire bell crank 59 includes a rearwardly extending arm 64 which frictionally engages the side of the presser bar sleeve 52, but only when the needle is in the rightmost position as illustrated in FIGS. 3 to 5. The end of the rearwardly extending arm is bent into a loop 67 so as not to present a sharp point. A forwardly extending arm 68 of the bell crank is disposed parallel to the front surface 70 of the collar, and a coil spring 71 having an eyelet 72 formed at its free end depends from a hole 73 in the bottom of the collar. The needle thread 74 is 3 threaded between the forwardly extending arm 68 of the bell crank 59 and the front surface 79 of the collar 57, through the hook-shaped thread guide 38, and then through the eyelet 72 of the coil spring 71.

When the needle is in its rightmost position as illustrated in FIGS. 3 to 5, the rearwardly extending arm 64 of the bell crank 59 frictionally engages the side of the presser bar sleeve 52 to pivot the bell crank so that the forwardly extending arm 63 nips the thread 74 against the front surface 70 of the collar 57. Nipping of the thread in conjunction with the coil spring 71 which acts as a thread take-up keeps the thread to the eye of the needle taut. Therefore, loops of thread cannot form at the eye of the needle for seizure by the hook beak 27 of the loop taker 26, and skipped stitches result.

When the needle is in its leftmost position as illustrated in FIGS. 1 and 2, since the rearwardly extending arm 64 of the bell crank 59 is out of contact with the side of the presser bar sleeve 52, the weight of the rearwardly extending arm 64, which is greater than that of the forwardly extending arm 68, pivots the bell crank 59 about its intermediate portion 61 until the rearwardly extending arm rests on a ledge 76 formed in the side of the collar 57. When the rearwardly extending arm 64 rests on the ledge 76 formed in the side of the collar, the forwardly extending arm 68 is pivoted away from the front surface 70 of the collar 57 to release the needle thread 74 so that stitches can be formed as usual.

Since stitches are formed only during the intermittent leftmost penetrations of the needle, a desirable long, loose basting stitch seam is formed. Such a basting stitch seam 77 is illustrated in FIG. 8 as formed in a portion of two plies 78 and 79 of fabric 81 by the skip stitch attachment 56 in combination with the blind-stitch pattern cam 46 which produces a plurality of rightmost needle penetrations for each leftmost penetration.

Although the invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been made by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention.

Having thus set forth the nature of the invention, what is claimed herein is:

1. A skip stitch attachment for a sewing machine having a frame, a needle bar mounted in the frame, means for imparting endwise reciprocating motion to the needle bar, means for jogging the needle bar laterally, a needle having an eye and connected to the exterior end of the needle bar, needle thread extending through the eye of the needle, a needle thread loop-engaging means mounted in the frame for cooperation with the needle, means for moving the needle thread loop-engaging means in timed relation with movement of the needle to form stitches, and a work feed mechanism mounted in the frame, said skip stitch attachment comprising a clamp, means for connecting the clamp to the needle bar, a bell crank having two arms, and means for pivotally mounting the bell crank on the clamp so that one arm contacts a portion of the sewing machine to rock the bell crank during the downstroke of the needle bar in one of its lateral positions to enable the other arm to nip the needle thread thus preventing the formation of a needle thread loop which is normally engaged by the needle thread loopengaging means to form a stitch.

2. The skip stitch attachment of claim 1 which includes an auxiliary needle thread take-up device.

3. The skip stitch attachment of claim 1 in which the means for jogging the needle bar laterally includes a means for producing stitches in which single crossover stitches are separated by pluralities of straight stitches and the arm of the bell crank contacts said portion of the sewing machine only during attempted formation of the straight stitches.

4. The skip stitch attachment of claim 1 in which a presser bar sleeve is mounted in the frame, a presser bar is mounted in the presser bar sleeve, a presser foot is connected to the exterior end of the presser bar, and the side of the presser bar sleeve is the portion of the sewing machine which is contacted by the arm of the bell crank.

5. The skip stitch attachment of claim 4 in which the presser bar sleeve is mounted behind the needle bar, the arm of the bell crank which contacts the side of the presser bar sleeve is a rearwardly extending arm and the other arm of the bell crank is a forwardly extending arm which is substantially horizontal and substantially parallel to the front surface of the clamp with the needle thread threaded between the forwardly extending arm and the front surface of the clamp.

6. The skip stitch attachment of claim 5 in which the rearwardly extending arm is so constructed as to make it pivot downwardly when not in contact with the side of the presser bar sleeve thus permitting free movement of the needle thread which is threaded between the forwardly extending arm and the front surface of the clamp and means are provided for limiting the downward movement of the rearwardly extending arm.

' 7. The skip stitch attachment of claim 5 in which the bell crank is formed from a single length of wire with an intermediate portion formed substantially parallel to the front surface of the clamp, and in which said intermediate portion is pivotally mounted on the clamp to serve as thefulcrum of the bell crank.

8. The skip stitch attachment of claim 7 in which the portion of the bell crank extending rearwardly from the intermediate portion weighs more than the portion of the bell crank extending forwardly from the intermediate portion so that the rearwardly extending arm will tend to pivot downwardly when not in contact with the side of the presser bar sleeve thus permitting free movement of the needle thread which is threaded between the forwardly extending arm and the front surface of the clamp, and means are provided for limiting the downward movement of the rearwardly extending arm.

9. The skip stitch attachment of claim 5 which includes an auxiliary needle thread take-up device including a resilient means depending from the bottom of the clamp and having an eyelet at its free end for the needle thread.

10. The skip stitch attachment of claim 9 in which the resilient means is a coil spring.

References Cited UNITED STATES PATENTS 2,853,036 9/1953 Enos 112262 X 2,862,468 12/1958 Johnson 112-158 I FOREIGN PATENTS 32,581 9/ 1957 Switzerland.

HERBERT F. ROSS, Primary Examiner. 

1. A SKIP STITCH ATTACHMENT FOR A SEWING MACHINE HAVING A FRAME, A NEEDLE BAR MOUNTED IN THE FRAME, MEANS FOR IMPARTING ENDWISE RECIPROCATING MOTION TO THE NEEDLE BAR, MEANS FOR JOGGING THE NEEDLE BAR LATERALLY, A NEEDLE HAVING AN EYE AND CONNECTED TO THE EXTERIOR END OF THE NEEDLE BAR, NEEDLE THREAD EXTENDING THROUGH THE EYE OF THE NEEDLE, A NEEDLE THREAD LOOP-ENGAGING MEANS MOUNTED IN THE FRAME FOR COOPERATION WITH THE NEEDLE, MEANS FOR MOVING THE NEEDLE THREAD LOOP-ENGAGING MEANS IN TIMED RELATION WITH MOVEMENT OF THE NEEDLE TO FORM STITCHES, AND A WORK FEED MECHANISM MOUNTED IN THE FRAME, SAID SKIP STITCH ATTACHMENT COMPRISING A CLAMP, MEANS FOR CONNECTING THE CLAMP TO THE NEEDLE BAR, A BELL CRANK HAVING TWO ARMS, AND MEANS FOR PIVOTALLY MOUNTING THE BELL CRANK ON THE CLAMP SO THAT ONE ARM CONTACTS A PORTION OF THE SEWING MACHINE TO ROCK THE BELL CRANK DURING THE DOWNSTROKE OF THE NEEDLE BAR IN ONE OF ITS LATERAL POSITIONS TO ENABLE THE OTHER ARM TO NIP THE NEEDLE THREAD THUS PREVENTING THE FORMATION OF A NEEDLE THREAD LOOP WHICH IS NORMALLY ENGAGED BY THE NEEDLE THREAD LOOPENGAGING MEANS TO FORM A STITCH. 